Chromosomal aberrations and mortality of x-irradiated mammalian cells: emphasis on repair.

Chromosomal aberrations induced by x-rays in synchronized Chinese hamster cells correlated well with mortality as the radiosensitivity was made to vary by a factor of 4 by treating the cells with colcemid or 5-bromodeoxyuridine and by irradiating the cells in different parts of the cell cycle. 37% survival was observed when the cells sustained about one aberration per cell. Furthermore, the positive correlation was observed during repair of damage. Repair was measured by the reduction in damage observed either as the incubation period between two doses was increased (repair of sublethal lesions), or as the cells were held at 20 degrees C after a single dose of radiation (repair of potentially lethal lesions). Repair of both sublethal and potentially lethal lesions occurred with a half-time of about 12 min and was inhibited at 0 degrees C. These correlations strongly support the hypothesis that x-ray-induced cell death results from damage in chromatin structures.